Axons terminating in lateral habenular nucleus (LHB) arise from the entopeduncular nucleus (feline homologue of media segment of globus pallidus of primates), lateral hypothalamus, preoptic region, and the interpeduncular nucleus. Convergence of limbic and basal ganglionic fibers on LHB suggests the nucleus may be important in the integration of somatic and visceral information. Functional studies implicate the habenula in olfactory and feeding behaviors, gastrointestinal motility, spinal motorneuron activity and endocrine secretion. The LHB will be studied to determine the extent of integration which occurs in the nucleus. The entopeduncular nucleus projects to a discrete region of LHB. Projections to LHB from preoptic region, lateral hypothalamus, and interpeduncular nucleus will be studied autoradiographically in cats to determine if there is also topographical organization of these afferents. To determine the degree of convergence of inputs on individual LHB neurons the regions afferent to LHB will be stimulated while recording extracellularly from LHB neurons. Efferents of LHB will be determined autoradiographically. To determine if there is topographical organization of LHB efferents, the retrograde transport of horseradish peroxidase will be studied following injections into regions in which LHB axons terminate. LHB efferents will be stimulated while recording from units antidromically activated in LHB to determine if individual axons project to more than one region. LHB afferents will be stimulated to orthodromically activate antidromically identified units to determine the degree of segregation of input-output pathways.